1. Field of the Invention
The present invention relates to a navigation apparatus for use on board a vehicle such as an automobile.
2. Description of the Related Art
Recent years have seen the development and commercial use of those on-board navigation apparatus. In such navigation apparatus, a plurality of points on the roads in road maps are digitized into map data for storage into a storage medium such as a CD-ROM. With the current location of the vehicle recognized by suitable means, a group of map data covering a certain geographical area including the current vehicle position is read out of the storage medium. The map data is shown on a display unit in the form of a map indicating the current vehicle position and its surroundings. The current vehicle position is automatically pointed to by a vehicle position mark on the displayed map.
Such conventional on-board navigation apparatus require the successive retrieval and feeding of map data about new areas in which the vehicle travels on. New map data needs to be read continuously from the storage medium. This means that if one map-containing storage medium driver were to also serve as a for a music driver storage medium, the frequent changing of the media required on the single driver would be very troublesome and impractical. The problem is circumvented by use of two separate drivers, one dedicated to playing the music and the other for driving map-containing recording media only. However, this solution, involving installation of a twin-driver arrangement in a limited space inside the vehicle, is cumbersome and expensive.
Another conventional solution to the above problem is to use a storage medium driver having a changer function. This driver accommodates a plurality of map and music-containing storage media, one of which is selectively reproduced as desired. One disadvantage of this solution is that every time map data is read from its storage medium, the music-containing storage medium must be interrupted from being reproduced, the interruption likely being frequent.